Surrey 108 (Harrison 5-31) and 52 for 3 trail Durham 421 by 261 runs
Two young Durham players, Jamie Harrison and Usman Arshad, bowled their side into a dominant position against Surrey, who are still 261 runs behind with seven wickets in hand after being made to follow on.
From 97 for 6 overnight, were only able to add 11 to their first-innings total. Their tail was mopped up by Harrison, a 22-year-old Lancastrian whose left-arm swing and seamers are delivered at a very brisk pace. He disposed of Surrey's last three batsmen, two lbw and finally scattering Jade Dernbach's stumps, without conceding a run.
It was Harrison's first five-wicket return in first-class cricket, taken in his first County Championship appearance this year. Steven Davies, easily Surrey's most impressive batsman in a poor team showing, stood firm amid the mayhem and finished unbeaten on 41, with his team 313 behind.
Harrison was a satisfied young man at the end of the day. He suffered a frustrating 2012 when he was hobbled by shin splints, and has worked hard on his fitness in the meantime. "All through the winter I was in the swimming pool at six in the morning and ten at night, and putting ice on my legs," he said. "That seems minimal when you take five wickets."
He has also put in a lot of overs, 350-plus, this summer for his club side Stockton and the Durham seconds, and the fitness dividend was clear to see.
With an eye on the weather forecast and trusting the bowlers who had served him so well in the first innings, Durham's captain, Paul Collingwood, enforced the follow-on and Harrison was immediately at it again, bowling Arun Harinath behind his legs for a duck. Rory Burns stood firm for three quarters of an hour but then Collingwood introduced Arshad and the innings took a new direction.
Arshad, 20, is making his first class debut, and he looks very useful. From Bingley, near Bradford, he has made his way northwards and impressed the Durham coaches with his performances in the second team this summer.
The absence of Ben Stokes with the England Lions has given him his opportunity and he grabbed it. He took two good wickets in Surrey's first innings, then two in two balls in the second. First he had Burns caught by Scott Borthwick at slip, then he tied up Vikram Solanki, who was caught behind down the leg side.
The day's play was restricted to 23 overs by rain and bad light. The decision by the umpires to take the players off in the late afternoon was not popular with the sparse crowd, and the light didn't appear at that time to offer any danger to batsmen or fielders. It became academic, however, when rain set in.
Harrison said that Durham were confident that, if the weather stays fair on Sunday and their bowlers stay patient, they will take the seven wickets they need for the win. He is probably right.